How do you sync music to iphone/ipad on a replacement computer?

Question

My old Win7 laptop crashed and I had no chance to de-authorize it in iTunes.  When I tried to sync my music to my iPhone via a replacement Win7 laptop, iTunes warned me that because I was attempting to sync to a new laptop that it would erase all music before copying my selections.  Okay, fine.   It erased everything and now iTunes refuses to copy ANY music to my iPhone.  I have looked in all help files for iTunes and iPhone, to no avail.  I hope someone else has already conquered this problem.

Answer 1

I solved this problem myself.  This problem was caused, not just by crashed laptop, but also because I had moved the windows media player based music folder to the 2nd hard drive on that laptop.  After the crash, I was able to use the DOS prompt to copy my data off the crashed laptop to the new laptop.  When I installed iTunes on the new laptop, it found the music folder and also the iTunes subfolder.  The iTunes folder must have config files the identify where the music is stored, so iTunes thought music was stored on a 2nd drive.  It could not find that location on the new laptop, so it could not sync anything to my iPhone.  iTunes would relocate individual files, but I could not find an automatic command to cause iTunes to relocate all files at once.  Apple Express Lane (one-time support for $29) was no help, other than to suggest I uninstall and reinstall iTunes and reload all my music from CD's into iTunes.
My solution: I did reinstall iTunes but I also deleted the iTunes music folder.  I then had to convert each music folder into iTunes files and redownload my iTunes purchases.  This took about 4 hours, but was still much quicker than reloading from CD's.  While that was in progress, I realized I should have tried deleting anything that looked like a config file in the iTunes music folder, rather than the whole folder.  Then maybe iTunes would have found the iTunes music files in the correct drive, avoiding the need to manually convert all files into iTunes.
I could not find a menu option or preference setting that would allow iTunes to automatically detect where the files were actually located in the iTunes folder.  If any one knows, please set me straight.  If not, I consider this a pretty serious defect in iTunes that it cannot overcome such a simple redirect as this.